Process for making graft copolymers

ABSTRACT

The present invention is directed to a method for forming graft copolymers from perfluoroolefins and perfluorovinyl ethers having fluorosulfonyl and fluorosulfonate functionality with selected polymers, and the uncrosslinked graft copolymers resulting therefrom.

FIELD OF THE INVENTION

[0001] The present invention is directed to a method for forming graftcopolymers from perfluoroolefins and perfluorovinyl ethers havingfluorosulfonyl and fluorosulfonate functionality with selected polymers,and the uncrosslinked graft copolymers resulting therefrom.

TECHNICAL BACKGROUND OF THE INVENTION

[0002] Howard, U.S. Pat. No. 5,798,417, discloses (perfluorovinylether)-grafted polyolefins. The grafting process involves contacting thepolymer in the form of a powder or a shaped article with a free-radicalinitiator and the monomer. The reaction medium is heterogeneous and thepolymer is invariably crosslinked during the grafting reaction. Thedegree of grafting varies with the initiator concentration and thereaction temperature. Up to 17 mol % incorporation of grafted monomer isclaimed (up to 9 mol % shown in the examples). The polymers are usefulas catalysts and as membranes in electrochemical cells.

[0003] U.S. Pat. No. 4,396,727 claims cation exchange membranes havingfluorovinyl sulfonic acid monomers grafted onto high molecular weightsubstrates. Grafting is carried out directly on films by using ionizingradiation. Substrate polymers have the following repeat units: CH₂—CXYwhere X is H, F, or CH₃, and Y is H or F. Polyethylene is the mostpreferred substrate. Solvents miscible with the monomer can be used toachieve thorough impregnation of the substrate. Graft ratios of up to75% are reported (although graft ratio is not defined, it is commonlyfound in the grafting literature as (w-w₀)/w₀ where w₀ is the weight ofthe substrate and w is the weight after grafting. So 75% graft ratio isequivalent to 43 weight % grafting). The membranes are useful inelectrochemical cells. U.S. Pat. No. 4,384,941 claims a process forelectrolysis of pure water using these membranes.

[0004] Drysdale et al., WO 98/31716 discloses free radical grafting ofpartially fluorinated functionalized vinyl monomers to polyethylene. Inthe process, the polyethylene is first dissolved and the graftingreaction takes place in solution. Incorporation of up to ca. 13 mol-% isachieved. The polymers are useful as molding resins, for coatings and ascatalysts.

[0005] DesMarteau, U.S. Pat. No. 5,463,005 discloses fluoromonomerscontaining sulfonimide groups and their copolymers withtretrafluoroethylene. Conductive compositions of these materials arealso disclosed.

[0006] Armand et al., EP 0,850,920 A2, teaches salts of perfluorinatedamides and their use as materials for ionic conduction. Polymerscontaining sulfonimide side groups are disclosed. Examples includeseveral condensation and addition polymers containing hydrocarbonbackbones.

[0007] Narang et al., U.S. Pat. No. 5,633,098 disclose ionic polymershaving sulfonic acid and sulfonimide functional groups. Polymersdisclosed include polysiloxanes, polymethacrylates, and poly(alkeneoxides).

[0008] Considerable interest has developed in the application offluorinated ionomers as solid polymer electrolyte membranes in secondarylithium batteries and fuel cells. Key to these applications is the useof fluorosulfonates or derivatives thereof as cation exchange groups. Itis believed that the cations associated with these functional groupsonly become sufficiently labile when highly electron-withdrawingfluorines are employed proximate to the sulfonate and sulfonatederivatives, typically, in groups represented by the formula —CF₂CF₂SO₃Hor —CF₂CF₂SO₃Li or sulfonyl imide or sulfonyl methide derivativesthereof. See for example Doyle et al., WO 9820573, Doyle et al., WO9941292(A1), Feiring et al., WO 9945048(A1).

[0009] Polymer having a backbone of methylene groups and pendant groupshaving the formula —CH₂CH₂—(CF₂)₂O(CF₂)₂SO₂F is prepared by a graftingreaction in Choi et al., WO 9952954.

[0010] The current state of the commercial art is exemplified by Nafion®Perfluoroionomer Membranes available from E. I. du Pont de Nemours andCompany, Wilmington, Del. Nafion® membranes were developed for thehighly corrosive environment of a chloralkali cell wherein the corrosionresistance of the perfluorinated ionomers is an important attribute. Itis believed that in certain other applications such as lithium batteriescorrosion resistance may be of less importance. In such a caseconsiderable reduction in materials cost may be achieved by reducing thefluorine content in parts of the molecule which do not affect ionicconductivity. See for example Choi et al., WO 9952954.

[0011] The present invention provides a method for combining aperfluorinated functional group with a polymer having a backbone whichcontains carbon hydrogen bonds with the aim of providing anon-cross-linked, highly processible lower cost ionomer of high ionicconductivity.

SUMMARY OF THE INVENTION

[0012] The present invention provides for a process comprising:

[0013] contacting a first polymer having a backbone which comprises atleast 50% methylene units with a solvent which swells or dissolves saidfirst polymer to form a solvent-swollen polymer or polymer solution;

[0014] contacting said solvent swollen polymer or polymer solution witha source of free-radicals and a compound of the formula F₂C═CFR¹R²SO₂Xwherein

[0015] R¹ represents a covalent bond or a perfluoroalkenyl radicalhaving 1 to 20 carbon atoms; R² is a radical of the formula:

—O—[CF₂CF(R³)—O_(m)]_(n)—CF₂CF₂—

[0016] wherein m=0 or 1, n=0, 1, or 2, and R³ is F or a perfluoroalkylradical having 1-10 carbons;

[0017] and X is F or the radical represented by the formula

—Y(M)(SO₂R⁴)_(p)

[0018] wherein Y is C or N, M is an alkali metal, R⁴ is a perfluoroalkylradical having 1-10 carbons optionally substituted with one or moreether oxygens, and p=1 or 2 with the proviso that p=1 when Y is N andp=2 when Y is C;

[0019] to form a reaction mixture;

[0020] providing sufficient heat to said reaction mixture to cause theinitiation of free-radical reaction; and, reacting said mixture to forma graft copolymer.

[0021] The present invention further provides for a non-crosslinkedpolymer comprising a polymer having a backbone which comprises at least50 mol-% methylene units and up to 50 mol-% of methylene units having apendant group comprising a radical represented by the formula

[0022] wherein R¹ represents a covalent bond or a perfluoroalkenylradical having 1 to 20 carbon atoms; R² is a radical of the formula:

—O—[CF₂CF(R³)—O_(m)]_(n)—CF₂CF₂—

[0023] wherein m=0 or 1, n=0, 1, or 2, and R³ is F or a perfluoroalkylradical having 1-10 carbons, and X is F, —OM, or the radical representedby the formula

—Y(M)(SO₂R⁴)_(p)

[0024] wherein Y is C or N, M is hydrogen or an alkali metal, R⁴ is aperfluoroalkyl radical having 1-10 carbons optionally substituted by oneor more ether oxygens, and p=1 or 2 with the proviso that p=1 when Y isN and p=2 when Y is C.

DETAILED DESCRIPTION

[0025] The present invention provides a process for preparingnon-crosslinked graft copolymers by reacting a perfluoro vinyl compoundcomprising a sulfonyl fluoride functionality or derivative thereof witha polymer in the presence of a free radical initiator and a suitablesolvent.

[0026] As used herein, the term “reacting” is intended to mean allowingat least two components in a reaction mixture to react to form at leastone product. “Reacting” may optionally include stirring and/or heatingor cooling.

[0027] In the process of the invention, the polymer is contacted with asolvent, which swells or, preferably, dissolves the polymer. The swollenpolymer or polymer solution is further contacted with a perfluorovinylcompound comprising a sulfonyl fluoride functionality or derivativethereof and a source of free radicals. Preferably the perfluorovinylcompound is soluble in the solvent which swells or dissolves thepolymer.

[0028] Polymers suitable for the process of the invention are thosewhich have hydrogens along the backbone which can be abstracted by afree radical initiator. Suitable are polymers having at least 50 mol-%of methylene units in the polymer backbone. Most olefinic type polymersare suitable; suitable olefinic type polymers may be fluorinated but notperfluorinated. Preferred are polyethylene, polypropylene, and theircopolymers, as well as copolymers of ethylene with acrylates,methacrylates, and vinyl acetate terpolymers thereof with olefins having3 or more carbons, and combinations thereof. Polyethylene is the mostpreferred.

[0029] Preferably, the source of free radicals is a free-radicalinitiator such as is well known in the art. Free radical initiatorssuitable for the process of the invention include inorganic peroxidesand organic peroxides and azo compounds. Organic peroxides arepreferred; tert-butyl peroxide and dicumyl peroxide are most preferred.The amount of initiator used is between 1 and 20 weight % of thepolymer, preferably from 5 to 10 weight %.

[0030] Fluorinated vinyl compounds containing a fluorosulfonyl fluoridefunctional group or a derivative thereof are suitable for the practiceof the invention. Suitable for the process of the invention areperfluorovinyl and perfluoroallyl ethers represented by the formulaF₂C═CFR¹R²SO₂X wherein R¹ represents a covalent bond or aperfluoroalkenyl radical having 1 to 20 carbon atoms; R² is a radical ofthe formula:

—O—[CF₂CF(R³)—O_(m)]_(n)—CF₂CF₂—

[0031] wherein m=0 or 1, n=0, 1, or 2, and R³ is F or a perfluoroalkylradical having 1-10 carbons; and X is F or the radical represented bythe formula

—Y(M)(SO₂R⁴)_(p)

[0032] wherein Y is C or N, M is an alkali metal, R⁴ is a perfluoroalkylradical having 1-10 carbons optionally substituted with one or moreether oxygens, and p=1 or 2 with the proviso that p=1 when Y is N andp=2 when Y is C.

[0033] Preferably R¹ is a bond or —CF₂—, R³ is a perfluoroalkyl radicalhaving 1-4 carbons, m=1, n=0 or 1, and X is F. Most preferably R¹ is abond, R³ is —CF₃ and n=1.

[0034] The grafting reaction is carried out by contacting theperfluorovinyl compound, which is usually a liquid at the reactiontemperature, with the polymer in the presence of the solvent. Thepolymer can be dissolved in a solvent or just swollen by the solvent.Higher incorporation of the monomers is achieved when the polymer iscompletely dissolved in the solvent. Suitable solvents include aromatichydrocarbons such as chlorobenzene and dichlorobenzene, halogenatedhydrocarbons, and polar aprotic solvents such as dimethyl acetamide anddimethyl formamide. Chlorobenzene is preferred.

[0035] In the preferred embodiment of the invention the graftingreaction is carried out by first dissolving or swelling the polyethylenein chlorobenzene at the reaction temperature, adding a fluorinated vinylcompound, preferably perfluoro(3,6-dioxa-4-methyl-7-octenesulfonylfluoride) (PSEPVE) and free-radical initiator, and stirring the mixtureunder an inert atmosphere. The concentration of chlorobenzene can rangefrom about 30% by weight in the swollen polymer to about 99% in apolymer solutions. Most preferred are solutions having polyethyleneconcentrations of 3 to 6% by weight. Reaction temperatures can betypically between room temperature and about 160° C. depending on thesolubility of the polymer and the decomposition temperature of theinitiator. The most preferred range is between 80 and 130° C. An inertatmosphere is necessary to avoid reaction of the free radicals withoxygen. Nitrogen and argon are suitable atmospheres.

[0036] According to the present invention, grafting occurs at themethylene units along the polymer backbone. However, stericconsiderations prevent grafting on nearby methylene units. Thus, in thepreferred embodiment wherein the backbone consists entirely of methyleneunits, a maximum degree of grafting is achieved with slightly more than20% of methylene units being subject to grafting. It is found in thepractice of the invention that the graft polymers obtained in thepreferred embodiment of the process of the invention contain from 10 to87 weight percent of the radical derived from the PSEPVE. The degree ofgrafting depends on the temperature and on the concentration of polymer,fluorinated vinyl compound, and initiator, as shown in the examplesbelow.

[0037] The graft polymers of the present invention not being crosslinkedexhibit excellent processibility. The non-ionic sulfonyl fluoride formsare melt processible by conventional means such as extrusion or molding,and are soluble in fluorinated solvents, aromatic hydrocarbons such aschlorobenzene, dichlorobenzene, toluene, and xylene, and halogenatedhydrocarbons such as tetrachloroethane. The ionic forms, such as theimides, methides, sulfonates, and sulfonic acids, of highly grafted lowMW polymers are soluble in water and methanol. This is in contrast tothe graft polymers of Howard, op. cit., which are crosslinked andtherefore insoluble.

[0038] The polymer produced by the process of the present invention isalso more uniformly grafted than in Howard. In the process of Howard,grafting occurs predominantly at surfaces of particles and shapedarticles. In the most preferred embodiment of the present invention,wherein the reaction is performed in solution, mixing of the reactantstakes place on the molecular scale, affording a considerable improvementin homogeneity.

[0039] In another embodiment, the process of the invention may beconducted by swelling porous particles of polymer in a mixture ofsolvent and fluorinated vinyl compound also containing free-radicalinitiator, and heating them below the melting point of the polymer. Asin the preferred embodiment hereinabove described, the degree ofgrafting depends on the ratio of fluorinated vinyl compound to solventas shown in the examples below. Suitable fluorinated vinyl compounds,solvents, and initiators are the same as hereinabove described above forthe preferred embodiment. In the present embodiment, reactiontemperatures should be kept below the lower of polymer melting point ordissolution temperature of the polymer in the reaction mixture.

[0040] The graft copolymers of the present invention can be processedinto films by known melt-processing methods as well as by solutioncasting methods. Tough transparent films are obtained by both methods.

[0041] The successful practice of the process of the invention dependsupon the dispersibility of the fluorinated vinyl compound within thesolvent-swollen or dissolved polymer. It is found in the practice of theinvention that the best results are obtained when the fluorinated vinylcompound is itself soluble in the solvent. When the fluorinated vinylcompound is not soluble in the solvent, obtaining a homogeneousdispersion of the fluorinated vinyl compound in the polymer is much moreproblematical. For this reason, it is preferred to perform the graftingreaction with the fluorinated vinyl compound in the form of a sulfonylfluoride, followed by hydrolysis to the sulfonate form or imidization ormethidization to the respective imide or methide form, as shown in thespecific embodiments provided. The sulfonate form can further beconverted to the sulfonic acid by acid exchange.

[0042] In a preferred embodiment, polyethylene is dissolved as describedhereinabove, and the resulting solution combined under the aboveconditions with a free radical initiator and a fluorinated vinylcompound represented by the formula F₂C═CFR¹R²SO₂X wherein R¹ is aperfluoroalkyl radical or a covalent bond, R² is a radical of theformula:

—O—[CF₂CF(R³)—O_(m)]_(n)—CF₂CF₂—

[0043] wherein m=0 or 1, n=0, 1, or 2, and R³ is F or a perfluoroalkylradical having 1-10 carbons; and X is F. More preferably R¹ is aperfluoroalkyl radical having 1-4 carbons or a covalent bond, m=1, n=0or 1, and R³ is a perfluoroalkyl radical having 1-4 carbons. Mostpreferably R¹ is a covalent bond, and R³ is —CF₃. The product so formedis the related graft copolymer in sulfonyl fluoride form.

[0044] The sulfonyl fluoride polymer obtained according to the preferredprocess of the invention can be transformed into ionomers by hydrolysisprocedures which are known in the art; see for example Doyle et al., WO9941292(A1). For example, the sulfonyl fluoride groups can betransformed to sulfonates by reacting with alkali metal hydroxidesolutions such as LiOH in water, water/methanol, and water/DMSO.Hydrolysis temperature ranges from room temperature to about 90° C.

[0045] While it is within the scope of the process of the invention tocombine an unsaturated disulfonyl imide or methide perfluorovinyl ether,such as described in Feiring et al., WO 9945048(A1) with the polymer,and perform the grafting reaction as hereinabove described, the limitedsolubility of the imide in ordinary solvents provides an incentive toperform the imidization, or methidization step, after the graftcopolymer is formed in the sulfonyl fluoride form.

[0046] In a preferred embodiment, in a second step, aperfluorosulfonamide is reacted with the sulfonyl fluoride form of thegraft copolymer in the presence of a base. Isolation of the polymer isnot necessary, and is less preferred, and the second step can beperformed immediately after grafting. High conversions are achieved.Triethylamine is the preferred base but other bases soluble in thereaction media can be used.

[0047] In a more preferred embodiment, triethylamine is used as the basein the second step of the reaction. Surprisingly, the imidized polymerso formed, obtained as the triethylammonium imide salt, is soluble andtractable, allowing films to be prepared either by casting from solutionor by melt processing. Transformation to the lithium salt is easilyachieved by reacting with lithium hydroxide solutions. Reactivesolutions include LiOH in water, water/methanol, and water/DMSO.Hydrolysis temperature ranges from room temperature to about 90° C. Thepolymer is less soluble in the lithiated form.

[0048] In a further embodiment of the process of the invention thepolymer can be isolated after the grafting reaction, and the second stepcarried out as described above on the purified polymer. The results arethe same. By this method other solvents and bases, that are notcompatible with the grafting reaction, can be used.

[0049] The non-ionic sulfonyl fluoride form of the graft polymersobtained by the process of the invention are not crosslinked andtherefore soluble in numerous organic solvents including aromatichydrocarbons such as chlorobenzene, dichlorobenzene, toluene, andxylene, and halogenated hydrocarbons such as tetrachloroethane. Theionic form of the graft polymers obtained by the process of theinvention are largely insoluble in most organic solvents, but are oflimited solubility in water and alcohols. However, it is observed in thepractice of the invention that when the triethylammonium imide is formedaccording to the process of the invention, the product stays in thereaction mixture. It is not known whether the mixture is a true solutionor a fine dispersion.

[0050] Any method known in the art for converting a small moleculehaving sulfonyl fluoride functionality to imide or methide has beenfound to be suitable for the practice of the process of the presentinvention for converting the sulfonyl fluoride form of the graftcopolymers of the present invention. Various methods are described inDes Marteau et al., Inorg. Chem., 1984, 23, 3720, Des Marteau et al.,Inorg Chem., 1990, 29, 2982, Canadian patent 2000142-A; U.S. Pat. No.4,505,997; and U.S. Pat. No. 5,072,040. Preferably, the sulfonylfluoride is contacted with a perfluorosulfonamide, preferablyperfluoromethylsulfonylamide, in the presence of triethylamine. Adescription of the preferred method is found in Hamrock et al., WO99/49529.

[0051] In a further embodiment, it is found that uncrosslinked sulfonylfluoride graft copolymers prepared according to the method of Drysdaleet al., op cit., are also converted at high yield according to the sameimidization procedures found to be effective for the sulfonyl fluorideform of the graft copolymers of the present invention. In a preferredembodiment, a polymer having methylene monomer units and a pendant grouphaving the formula

—CH₂—CH₂—CR⁵R⁶R⁷X

[0052] wherein R⁵ and R⁶ are each independently fluorine orperfluoroalkyl, R⁷ is fluorinated alkylene optionally containing etheroxygen and X is —SO₂F, is contacted with perfluorosulfonamide,preferably perfluoromethylsulfonylamide, in the presence oftriethylamine to form the associated imide which may then be readily ionexchanged to form the lithium ionomer useful in batteries.

[0053] When forming the ionic species of the invention, namely thesulfonates, sulfonic acids, imides and methides as herein described, themethods employed in the art for small molecules rather than polymers maybe employed. However, solubility considerations make the reactions moreproblematical. The solvents typically used for these reactions withsmall molecules are polar aprotic solvents such as acetonitrile, THF,diethyl ether, DMSO. Most of these do not appreciably dissolve thesulfonyl fluoride form of the graft copolymers of the invention, andtherefore are less preferred. Preferred instead are chlorobenzene,dichlorobenzene and toluene.

[0054] Stability is a further concern in the particular case wherein thepolymer backbone comprises monomer units of vinylidene fluoride.Polyvinylidene fluoride is known to be unstable to bases; the methods ofthe art for forming imides when applied to a graft copolymer ofpolyvinylidene fluoride result in degradation of the backbone chain.

[0055] Once conversion to the imide or methide form is accomplishede.g., to form the triethylammonium imide or methide, the lithium imideor methide may be formed according to ordinary ion exchange means as iswell known and widely practiced in the art, and as hereinabovedescribed.

[0056] Ionomers prepared by this process are useful for electrochemicalapplications such as batteries, fuel cells, electrolysis cells, ionexchange membranes, sensors, or electrodes.

EXAMPLES Example 1 Grafting of PSEPVE onto Polyethylene in Solution

[0057] A 500 mL 3-neck round bottom flask, provided with condenser, gasinlet, thermocouple, addition funnel, and magnetic stirring was chargedunder N₂ atmosphere with the following: 10 grams of polyethylene(Novapol® low density polyethylene from NOVA Chemicals of Calgary, AB,Canada), 300 mL of chlorobenzene (Aldrich), and 20 grams of PSEPVE madeaccording to Connolly et al., U.S. Pat. No. 3,282,875. The flask wasplaced in an oil bath at 90° C. and the mixture was stirred until all ofthe polyethylene dissolved. Then, a solution of 1 g benzoyl peroxide in20 mL of chlorobenzene was added drop-wise through the addition funnelduring a one hour period. The reaction mixture was stirred continuouslyat 90° C. for a total of 6 hours.

[0058] After the reaction time, the mixture was diluted with 80 mL ofchlorobenzene and precipitated into methanol. The polymer obtained wasfiltered through a glass fritted funnel and washed with methanol. It wasfurther extracted in a soxhlet apparatus with acetone for a total of 10hours. Finally, it was dried overnight under vacuum at 50° C. 13.6 g ofpolymer were obtained, with 26.7 weight-% incorporation of PSEPVE asdetermined by ¹H NMR and elemental analysis.

[0059] The procedures of Example 1 were repeated in Examples 2-15 withsome variation in the quantities of materials, temperature, initiator,solvent and time, as indicated in Table 1. Results are summarized inTable 1. Examples 10, 11, 12, 13 all came from the same reaction. Theywere taken out of the reaction mixture at different times to followconversion. TABLE 1 Preparation of PSEPVE- grafted polyethylene Chloro-t-Butyl PSEPVE Example Polymer PSEPVE benzene Peroxide Time TemperatureYield incorporation No. (g) (g) (mL) (g) (h) (° C.) (g) (weight %) 1 1020 300  1** 6  90 13.6 26.7 2 10 11 120* 1 24  120 16.4 39.0 3 10 15120* 1 8 120 17.9 44.2 4 10 15 320* 2 8 120 19.1 47.7 5 10 15 320* 2 8120 19.9 49.7 6 10 15 320 2 6 120 20.2 50.4 7 10 20 200* 1 24  120 20.952.1 8 10 20 300 2 8 120 26.8 62.7 9 10 20 300* 2 24  120 30.0 66.6 1010 50 300 2 3 126 NA 68.0 11 10 50 300 2 4 126 NA 72.0 12 10 50 300 2 6126 NA 74.8 13 10 50 300 2 9 126 NA 76.6 14 10 50 300 2 20  125 43.877.3 15  5 50 150 2 6 126 38.1 86.9

[0060] Films of the graft polymers were prepared from the melt in aPasadena Hydraulics model SP 215C press at 140° C. and 30,000 lbs. Filmswith thickness between 5 and 10 mils were prepared. The films werehydrolyzed to the lithium form by immersing them in a 1M LiOH solutionin Water/DMSO (1/1 by volume) at 80° C. for several hours. After rinsingwith DI water, they were dried in a vacuum oven at 90-100° C. for 48 to72 hours. FTIR indicated complete hydrolysis of the films.

[0061] Ionic conductivity was measured on these films swollen withpropylene carbonate (PC), and a 1:1 mixture of ethylene carbonate (EC)and dimethyl carbonate (DMC). The dried hydrolyzed films were soaked inexcess solvent for several hours and allowed to attain maximum swelling(typically 5 hours for most samples). The films were then removed fromthe liquid, blotted with a paper towel to remove excess solvent, andtested. Conductivity was determined using the four-point probe techniquedescribed in Doyle et al., WO 9820573(A1), which is incorporated hereinby reference. TABLE 2 Ionic conductivity of PSEPVE- grafted polyethylenePC EC/DMC Example Weight % mol % Repeat Conduct. Conduct. No. PSEPVEUnits grafted (S/cm) (S/cm) 1 26.7 2.3 1.50E-05 2.34E-05 2 39.0 4.09.67E-05 6.44E-05 3 44.2 5.0 2.18E-04 2.07E-04 4 47.7 5.7 2.89E-042.41E-04 5 49.7 6.2 2.53E-04 2.56E-04 6 50.4 6.4 2.79E-04 2.08E-04 752.1 6.8 2.87E-04 2.85E-04 8 62.7 10.5 4.28E-04 9 66.6 12.4 6.60E-04 1068.0 13.3 2.48E-04 11 72.0 16.0 4.17E-04 12 74.8 18.5 3.20E-04 13 76.620.5 4.21E-04 14 77.3 21.0 4.56E-04

Examples 16-19 Grafting of PSEPVE onto Polyethylene in a Swollen State

[0062] Four 50 mL Schlenk tubes were each charged with the following: 5g of porous polyethylene granules (Spherilene® linear low densitypolyethylene from Montell USA Inc. of Wilmington, Del.), 0.5 g oft-butyl peroxide (Aldrich), and 5 mL PSEPVE. In addition three of thetubes were charged with 3, 5, and 10 mL quantities of chlorobenzene. Thetubes were evacuated and purged with nitrogen four times and then heatedto 120° C. for 8 hours under nitrogen atmosphere. After cooling to roomtemperature the polymer granules were filtered off and placed in soxhletextractors where they were extracted with acetone for 8 hours to removeany traces of monomer or solvent. Finally the samples were dried in avacuum oven at 60° C. for 48 hours.

[0063] Under these reaction conditions the polymer granules did notdissolve in the reaction mixture but were swollen to different extents.The amount of grafted monomer increased dramatically by using a smallamount of solvent. The results are shown in Table 3. TABLE 3 Grafting ofPSEPVE onto polyethylene in the solid state PSEPVE/ PSEPVE ExampleChlorobenzene incorporation mol % Repeat Polymer Tm No. (mL/mL) (weight%) Units grafted (° C.) 16 5/0 23.3 1.9 126 17 5/3 51.1 6.5 117 18 5/551.6 6.7 116 19  5/10 54.9 7.6 113

Example 20

[0064] A 600 mL stainless steel Parr pressure reactor (from ParrInstrument Co, Moline, Ill.) was charged with 10 g of polyethylene(Novapol® low density polyethylene from NOVA Chemicals of Calgary, AB,Canada), 200 mL of o-dichlorobenzene (Aldrich), and 15 g ofperfluoro(3-oxa-4-pentene sulfonyl fluoride) prepared according to themethod described in Ezzell et al., U.S. Pat. No. 4,358,545. The reactorwas purged and vented three times with nitrogen (100 psig) and thenheated to 120° C. for 1 hour under autogenous pressure (˜15 psig) todissolve the polyethylene. Then a solution containing 2 g of t-butylperoxide in 50 mL of o-dichlorobenzene was pumped into the reactor at0.5 mL/min. The reaction mixture was stirred at 500 rpm and 120° C. fora total of 8 hours. Finally the reactor was allowed to cool down andremain overnight at room temperature without stirring.

[0065] After discharging the reactor, the reaction mixture was firstheated to redissolve the polymer and then it was precipitated intomethanol. The precipitated material was filtered off and extracted in asoxhlet extractor with acetone for 6 hours. Then it was dried in avacuum oven at 50° C. for 48 hrs.

[0066] The polymer obtained was further purified by dissolving it intoluene and precipitating into methanol. After filtering it and drying17.7 g of graft polymer were obtained. The polymer contained 9 mol % ofgrafted perfluorosulfonyl fluoride monomer as determined by ¹H NMR andelemental analysis. It had average molecular weights Mn=18,600 andMw=75,300 as determined by Size Exclusion Chromatography intrichlorobenzene at 135° C. DSC analysis of the polymer showed a glasstransition temperature at −22° C., and a melting transition at 99° C.with a heat of fusion of 28 J/g.

[0067] A film of this material was prepared and hydrolyzed as describedabove in Example 1. In PC it swelled 251% and had a conductivity of3.21E-04 S/cm while in a 1:1 mixture of EC/DMC it swelled 184% and had aconductivity of 4.12E-04 S/cm.

Examples 21-24 Grafting of PSEPVE onto Copolymers of Ethylene andMethacrylic Acid

[0068] A 500 mL 3-neck round bottom flask fitted with condenser, gasinlet, thermocouple, addition funnel, and magnetic stirring was chargedunder N₂ atmosphere with 10 grams of an ethylene copolymer withmethacrylic acid (Nucrel® 0407 from E. I. du Pont de Nemours and Companyof Wilmington, Del.), and 250 mL of chlorobenzene (Aldrich). The flaskwas placed in an oil bath at 120° C. and the mixture stirred until thepolymer dissolved. After adding 20 g of PSEPVE to the reaction mixture,a solution of 2 g of t-butyl peroxide in 50 mL of chlorobenzene wasadded drop-wise through the addition funnel during a 45 min period. Thereaction mixture was continued to stir at 120° C. for a total of 8hours.

[0069] After the set reaction time, the mixture was poured into a largeexcess of methanol. The precipitated polymer was filtered off, washedwith methanol, and dried in a vacuum oven at 70° C. for 24 hours. 23.3 gof polymer were obtained.

[0070] This reaction was repeated under the same conditions using othergrades of Nucrel® resins containing different amounts of methacrylicacid. The grafting of fluoromonomer decreased with increased content ofmethacrylic acid in the copolymer. Results of these reactions are shownin Table 4. TABLE 4 Grafting of PSEPVE onto copolymers of ethylene andmethacrylic acid Example Methacrylic Acid in Yield of grafting PSEPVEgrafted No. Copolymer (weight %) reaction (g) (weight %) 21 4.0 23.3 5722 8.7 22.2 55 23 8.7 20.8 52 24 20.0  14.6 32

[0071] Films of these polymers were prepared and hydrolyzed as describedabove in Example 1. A film of sample E93888-46 swelled 126% in PC andhad an ionic conductivity of 3E-04 S/cm.

Examples 25-30 Grafting of PSEPVE onto Block Copolymers of Styrene andEthylene/butylene

[0072] A 500 mL 3-neck round bottom flask fitted with condenser, gasinlet, thermocouple, addition funnel, and magnetic stirring was chargedunder N₂ atmosphere with 10 grams of copolymer (Kraton® D1101 from ShellOil Co. of Houston, Tex.) and 300 mL of chlorobenzene (Aldrich). Theflask was placed in an oil bath at 120° C. and the mixture stirred untilthe polymer dissolved. After adding 20 mL of PSEPVE to the reactionmixture, a solution of 2 g of t-butyl peroxide in 20 mL of chlorobenzenewas added drop-wise through the addition funnel during a 1 hour period.The reaction mixture was stirred at 120° C. for a total of 8 hours.

[0073] After the reaction time, the mixture was poured into a largeexcess of methanol. The precipitated polymer was filtered off, washedwith methanol, and dried in a vacuum oven at 50° C. for 24 hours. It wasfurther purified by dissolving it in chloroform and precipitating intomethanol. After filtering and drying 23.5 g of polymer were obtained.

[0074] This reaction was repeated under the same conditions using othergrades of Kraton® resins containing different styrene/rubber (S/R)ratios. Results of these reactions are shown in Table 5. TABLE 5Grafting of PSEPVE onto block copolymers of styrene andethylene/butylene PSEPVE % Conduc- Exam- Polymer PSEPVE Grafting graftedSwell tivity ple S/R added yield (weight in (S/cm) No. ratio (mL) (g) %)Water In Water 25 13/87 10 15.5 35.5 171 5.63E-03 26 13/87 15 16.9 40.7356 3.07E-03 27 29/71 15 21.7 53.8 360 2.88E-03 28 29/71 20 23.5 57.4 NANA 29 33/67 15 19.6 48.9 318 3.82E-03 30 33/67 20 22.5 55.6 NA NA

[0075] Films of the graft block copolymers were prepared from the meltin a Pasadena Hydraulics model SP 215C press at 130° C. and 30,000 lbs.Films with thickness between 5 and 10 mils were made. The films werehydrolyzed to the lithium form by immersing them in a 1M LiOH solutionin water/methanol (1/1 by volume) at 75° C. for two hours. After rinsingwith DI water, they were dried in a vacuum oven at 90-100° C. for 48 to72 hours. Ionic conductivity of these films was measured as describedabove in Example 1. Conductivity in water is shown in Table 5 and is inthe order of 10⁻³ S/cm for all samples.

Example 31 Synthesis of PSEPVE-imide Grafted Polyethylene

[0076] A 500 mL 3-neck round bottom flask, equipped with a condenser,magnetic stirring, addition funnel, gas inlet, and under nitrogenatmosphere was charged with 8.0 grams of polyethylene (Novapol® lowdensity polyethylene from NOVA Chemicals of Calgary, AB, Canada) and 100mL of chlorobenzene (Aldrich). The flask was placed in an oil bath at125° C. and the mixture stirred until the polyethylene dissolved. Afteradding 15 g of PSEPVE to the reaction mixture, a solution of 0.5 g oft-butyl peroxide (Aldrich) in 25 mL of chlorobenzene was added drop-wisethrough the addition funnel over 30 minutes. The mixture was stirred at125° C. for a period of 6 hours. After this time, the temperature waslowered to 70° C. and 10 mL of triethylamine were added. Then 5.0 gramsof trifluoromethanesulfonamide (TCI America, Portland, Oreg.) were addedin small portions using a powder addition funnel and the mixture wasstirred for 24 hours at 70-80° C.

[0077] After the reaction time the mixture was poured into a largeexcess of methanol and the precipitated polymer was filtered, washed anddried in a vacuum oven at 60° C. for 48 hrs. 18.5 g of graft polymerwere obtained. ¹H NMR of this polymer indicates that 6.1% of thepolyethylene repeat units are grafted and ¹⁹F NMR shows that more that90% of the sulfonyl fluoride groups were converted to sulfonimide. DSCanalysis of the polymer showed a glass transition temperature at 4° C.,and a melting transition at 102° C. with a heat of fusion of 26 J/g.

[0078] A film was prepared from the melt by pressing a sample of thepolymer in a Pasadena Hydraulics model SP 215C press at 140° C. and30,000 lbs for 5 min. The film was transformed to the lithium salt formby immersing it in a 0.5M LiOH solution in water/methanol (1/1 byvolume) at 60° C. for two hours. After rinsing with DI water, it washeated in DI water at 80° C. for an additional two hours and then it wasdried in a vacuum oven at 80° C. for 24 hours. The dried hydrolyzed filmwas soaked in excess propylene carbonate (PC) for several hours andallowed to attain maximum swelling. It was then removed from the liquid,blotted with a paper towel to remove excess solvent, and tested forionic conductivity. The film absorbed 326% of its weight in PC and had aconductivity of 7.59×10⁻⁴ S/cm.

Example 32 Synthesis of PSEPVE-imide Grafted Polyethylene in Two Steps

[0079] A 500 mL 3-neck round bottom flask, equipped with a condenser,magnetic stirring, addition funnel, gas inlet, and under nitrogenatmosphere was charged with 10.0 grams of polyethylene (Novapolμ® lowdensity polyethylene from NOVA Chemicals of Calgary, AB, Canada) and 250mL of chlorobenzene (Aldrich). The flask was placed in an oil bath at126° C. and the mixture stirred until the polyethylene dissolved. Afterthe polymer dissolved 40 grams of PSEPVE were added and then a solutionof 2 g of t-butyl peroxide in 50 mL of chlorobenzene was added drop-wiseover a period of 60 minutes. The mixture was stirred at 126° C. for 2additional hours. After the reaction time the mixture was poured into alarge excess of methanol. The precipitated polymer was filtered, washedand dried overnight under vacuum at 70° C. 33.9 g of polymer wereobtained. The polymer contained 14% of the repeat units grafted withperfluorosulfonyl fluoride monomer as determined by ¹H NMR. It hadaverage molecular weights Mn=10,200 and Mw=98,500 as determined by SizeExclusion Chromatography in trichlorobenzene at 135° C. DSC analysis ofthe polymer showed a glass transition temperature at −30° C., and amelting transition at 102° C. with a heat of fusion of 14 J/g.

[0080] 20.0 grams of the polymer prepared above and 150 mL of anhydrouschlorobenzene (Aldrich) were charged under nitrogen atmosphere into a250 mL 3-neck round bottom flask, equipped with a condenser, magneticstirring, addition funnel, and gas inlet. The flask was placed in an oilbath at 80° C., and after the polymer dissolved, 15 mL of triethylaminewere added. Then 5 g of trifluoromethanesulfonamide (TCI America,Portland, Oreg.) were added in small portions using a powder additionfunnel and the reaction mixture stirred at 80° C. for 24 hrs.

[0081] After the set reaction time, the mixture was poured intomethanol. The precipitated polymer was filtered, washed and driedovernight under vacuum at 65° C. 20.2 grams of polymer were obtained. ¹Hand ¹⁹F NMR showed that more than 90% conversion of the sulfonylfluoride to sulfonimide was achieved.

What is claimed is:
 1. A process comprising contacting a polymer havinga backbone which comprises at least 50% methylene units with a solventwhich swells or dissolves said polymer to form a solvent-swollen polymeror polymer solution; contacting said solvent swollen polymer or polymersolution with a source of free-radicals and a compound of the formulaF₂C═CFR¹R²SO₂X wherein R¹ represents a covalent bond or aperfluoroalkenyl radical having 1 to 20 carbon atoms; R² is a radical ofthe formula: —O—[CF₂CF(R³)—O_(m)]_(n)—CF₂CF₂— wherein m=0 or 1, n=0, 1,or 2, and R³ is F or a perfluoroalkyl radical having 1-10 carbons; and Xis F or a radical represented by the formula —Y(M)(SO₂R⁴)_(p) wherein Yis C or N, M is an alkali metal, R⁴ is a perfluoroalkyl radical having1-10 carbons optionally substituted with one or more ether oxygens, andp=1 or 2 with the proviso that p=1 when Y is N and p=2 when Y is C; toform a reaction mixture; providing sufficient heat to said reactionmixture to cause the initiation of free-radical reaction; and, reactingsaid mixture to form a graft polymer.
 2. The process of claim 1 whereinthe polymer further comprises monomer units selected from the groupconsisting of olefins, acrylates, vinyl acetates, styrenes, andfluorinated mixtures thereof, but not perfluorinated derivatives thereofand mixtures thereof.
 3. The process of claim 2 wherein the polymer isselected from the group consisting of polyethylene, polypropylene,ethylene acrylic acid copolymers, ethylene vinyl acetate copolymers,ethylene styrene copolymers, terpolymers thereof with olefins having 3or more carbons, and combinations thereof.
 4. The process of claim 1wherein the polymer is polyethylene.
 5. The process of claim 1 whereinthe solvent is selected from the group consisting of chlorobenzene,dichlorobenzene, halogenated hydrocarbons, dimethyl acetamide anddimethyl formamide.
 6. The process of claim 5 wherein the solvent ischlorobenzene.
 7. The process of claim 1 conducted in a polymersolution.
 8. The process of claim 7 conducted in a solution of 3% to 6%by weight of polyethylene in a chlorobenzene solution.
 9. The process ofclaim 1 wherein R¹ is a covalent bond or —CF₂—.
 10. The process of claim1 wherein m=1, n=0 or 1, and R³ is —CF₃.
 11. The process of claim 1wherein X is F.
 12. A non-crosslinked polymer comprising a polymerhaving a backbone which comprises at least 50 mol-% methylene units, anda pendant group comprising a radical represented by the formula

wherein R¹ represents a covalent bond or a perfluoroalkenyl radicalhaving 1 to 20 carbon atoms; R² is a radical of the formula:—O—[CF₂CF(R³)—O_(m)]_(n)—CF₂CF₂— wherein m=0 or 1, n=0, 1, or 2, and R³is F or a perfluoroalkyl radical having 1-10 carbons, and X is F, —OM,or a radical represented by the formula —Y(M)(SO₂R⁴)_(p) wherein Y is Cor N, M is hydrogen or an alkali metal, R⁴ is a perfluoroalkyl radicalhaving 1-10 carbons optionally substituted by one or more ether oxygens,and p=1 or 2 with the proviso that p=1 when Y is N and p=2 when Y is C.13. The polymer of claim 12 further comprising up to 50 mol-% of monomerunits selected from the group consisting of olefins, acrylates, vinylacetates, styrenes, and combinations thereof.
 14. The polymer of claim12 having 100 mol-% of methylene units.
 15. The polymer of claim 12wherein R¹ is a covalent bond or —CF₂—.
 16. The polymer of claim 12wherein m=1, n=0 or 1, and R³ is —CF₃.
 17. The polymer of claim 12wherein X is F.
 18. The polymer of claim 12 wherein X is —OM, or aradical represented by the formula —Y(M)(SO₂R⁴)_(p) wherein Y is C or N,M is hydrogen or an alkali metal, R⁴ is a perfluoroalkyl radical having1-10 carbons optionally substituted by one or more ether oxygens, andp=1 or 2 with the proviso that p=1 when Y is N and p=2 when Y is C. 19.The polymer of claim 18 wherein X is —OM where M is hydrogen or analkali metal.
 20. The polymer of claim 18 wherein X is a radicalrepresented by the formula —Y(M)(SO₂R⁴)_(p) wherein Y is C or N, M ishydrogen or an alkali metal, R⁴ is a perfluoroalkyl radical having 1-10carbons optionally substituted by one or more ether oxygens, and p=1 or2 with the proviso that p=1 when Y is N and p=2 when Y is C.
 21. Thepolymer of claim 20 wherein Y is N, p=1, and R⁴ is a perfluoroalkylradical having 1-4 carbons.
 22. The polymer of claim 21 wherein Y is C,p=2, and R⁴ is a perfluoroalkyl radical having 1-4 carbons.
 23. Thepolymer of claim 18 wherein M is Li.
 24. The polymer of claim 20 whereinM is Li.
 25. A non-crosslinked polymer comprising a polymer having abackbone which comprises at least 50 mol-% methylene units, and apendant group comprising a radical represented by the formula—CH₂—CH₂—CR⁵R⁶R⁷X wherein R⁵ and R⁶ are each independently fluorine orperfluoroalkyl, R⁷ is fluorinated alkylene optionally containing etheroxygen, and X is a radical represented by the formula —Y(M)(SO₂R⁴)_(p)wherein Y is C or N, M is hydrogen or an alkali metal, R⁴ is aperfluoroalkyl radical having 1-10 carbons optionally substituted by oneor more ether oxygens, and p=1 or 2 with the proviso that p=1 when Y isN and p=2 when Y is C.
 26. The polymer of claim 25 further comprising upto 50 mol-% of monomer units selected from the group consisting ofolefins, acrylates, vinyl acetates, styrenes, and combinations thereof.27. The polymer of claim 26 having 100 mol-% of methylene units.
 28. Thepolymer of claim 26 wherein M is lithium.
 29. The polymer of claim 26wherein Y is N, p=1, and R⁴ is perfluoralkyl having 1-4 carbons.
 30. Thepolymer of claim 26 wherein Y is C, p=2, and R⁴ is perfluoralkyl having1-4 carbons.
 31. An ionically conductive composition comprising thepolymer of claim 12 or claim 25 and an organic carbonate.
 32. Theionically conductive composition of claim 31 wherein the organiccarbonate is a mixture of ethylene carbonate and dimethyl carbonate.